Cutting instruments or edged tools have been used by many types of people and industries for hundreds of years: all of them needing an edge that separates matter or simply cuts, be they crafts people, butchers, hunters, carpenters, warriors, law enforcement personnel or others. Edged tools allow for civilizations to grow and expand through the work that cutting tools enable us to do. Civilization depends on the act of cutting things. Over time these edged tools have gone from simple fixed blades, sometimes with big blades to easily transportable folding cutting tools: the folder being smaller in overall size than a fixed blade cutting tool. Folding meaning that the cutting edge or blade is able to fold or pivot into an enclosed handle or holster that encapsulates the sharp blade within the actual handle of the knife itself. A knife or edged tool with its own traveling encapsulated holster is such an example. This folding position allows for a smaller profile overall, safe carry, safe handling and transport of the cutting edged tool because the cutting edge is safely encapsulated within the handle with no exposed cutting edge. There are two possible positions of a folding knife: the first being that where the blade is closed or enclosed inside the handle and the second is where the blade is fully extended or open with its cutting edge exposed, thus allowing cutting work to be done.
Folding knives have become very popular because of their convenience of carry and use. The problem with folding knives is that unlike a fixed blade that cannot close onto ones fingers or hands while in use, a folding knife is by design constructed to fold, and can fold inadvertently and will close inadvertently if not prevented to by some sort of locking mechanism. Inadvertent folding or closing of a folding knife blade during use can lead to severe disfigurement and or loss of one's fingers and hand. Such inadvertent folding or closing can be a dangerous situation and many an old style slip joint folding knives were and are thought of as non working tools or dress knives because of the lack of a proper and safe locking mechanism: these tools are only used to do minor functions, not real work, because any undue pressure on the back of the blade will cause it to close. One can only put cutting pressure on the blade's front edge as back pressure or twisting can cause the blade to close on one's fingers. The second major issue with folding knives is that one needs a detent or indent or catch mechanism to hold the blade closed safely within the handle thereby only allowing the blade to come out or be exposed at the users demand or need. In other words knives need to be open or closed at the user's discretion not at the whim of the knife or situation that might arise.
Over the years many types of locking mechanisms and detents have been tried to keep the folding knifes blade either safely within the handle while closed or to keep it fully extended while the blade is exposed for use to prevent inadvertent closure of the blade. One of the oldest types and most commonly known of the simple locking mechanisms was the standard back lock mechanism. In a back lock mechanism, a longitudinal piece of a rigid material, such as steel or other metal or plastic, pivots around a pivot point near the forward portion of the back lock. By applying pressure to the rearward portion of the locking mechanisms lever, a forward portion rotates around the point (like a lever and a fulcrum action) releasing a tang type engagement from the upper part of the heel of the blade.
The heel includes a small shelf or step for the tang to set on top of. When the tang disengages, the blade is now allowed to pivot around from an open position to a closed position within the handle. Although it is simple to make and use, it is a simple lever and fulcrum action. To activate the fulcrum one only needs pressure on the end of the lever. As Archimedes posed, given a lever of sufficient length and a fulcrum to anchor it, the world can be moved. The problem with this is that the further one is from the fulcrum, the greater the length of the lever or the greater the force applied and the back lock is prone to fail, sometimes with catastrophic effect when excessive pressure is applied to the upper back edge of the exposed knife blade. Since within normal use or hard use of an edged tool, the user encounters this type of force either by direct or indirect action of the user, the back lock is a not a good choice of locking mechanism. This mechanism also rides under the user's hand and inadvertently one might disengage the lock with normal pressure of one's hands leading to the blade closing on one's fingers.
Another type of locking mechanism commonly used is called a liner lock. The liner lock is generally comprised of a leaf spring, usually made of metal which is part of the inside liner of the knife handle, hence its name, and it is interconnected with the liner and the handle with a section of the liner being cut to match the butt end of the knife blade. When the knife blade is exposed and the knife opened to an extended position, the forward edge of the cut end of the liner extends outward in an arc from the inside of the liner scale and positions itself behind the butt or heel of the blade. The contact that keeps the blade in an exposed or open position is the limited contact between the tang cut end of the liner and the heel or butt end of the knife. Liner locks tend to fail because of the “law of arcs” and position of the locking steel tang itself, which must always be at a set distance from its central pivot. The tang arms of the liner in coming out from the scale located within the handle cavity, must follow a pivot point and the tang cut end of the liner must travel in an arc, therefore, it cannot make full contact with the heel of the blade. Over the years people have tried to angle cut the butt or heel of the blade to encourage more contact with the tang cut end of the liner. The liner lock actually only contacts the heel or butt of the blade on the leading edge of the tang cut arm or the trailing edge of the tang cut arm. When one or both of these wear out or round off, catastrophic failure occurs and the lock fails to hold or lock the blade exposed or open, the lock inadvertently fails, and the folding knife actually folds and closes. The liner lock is also prone to failure due to excessive pressure on the back of the exposed blade. Under excessive pressure the liner lock has a tendency to bow or otherwise deform, due to the extended length of the liner lock and the nature of the material required to fit within the knife handle itself. The liner lock is so prone to failure that many liner locks now have additional locking mechanisms or pieces that have been invented to block the movement of the liner across the butt of the knife and serve to lock the liner lock. The liner lock also has a problem where the knife must be taken out of use position to disengage the lock and the lock release rides by one's index finger and under duress as with firearms, one tends to flex one's index finger releasing the blade. In firearms this involuntary motion gives us a negligent discharge.
Another type of lock is the compression lock which has three parts that must work in unison to function: a liner tang or ball, an anvil pin and a shelf for the tang or ball to rest on. It uses a compressive force generated over a short distance to lock the blade with a liner tang or a ball between the blade stop pin and a shelf or step on the heel of the blade. The configuration of the blade locking mechanism in theory would substantially stop the blade from failing or allowing inadvertent closing of the blade during use. When force is applied to the upper part of the blade commonly known as the back of the blade, the non-cutting surface, the tang of the knife locking mechanism is compressed between the anvil end of the knife blade and the anvil pin or stop pin located in the top of the handle. The compression lock would appear to be very strong but has several draw backs and points of immediate concern of failure. The compression lock is only as strong as the tiny screws that actually hold the anvil pin or stop pin into the sides of the scales or knife handle. If the screws fail from metal fatigue, a common problem in metal receiving constant vibration or impact, or work themselves loose, the stop/anvil pin will fall out and the blade will rotate completely around the back side of the blade as there will be no compression surface to compress against. The anvil pin itself must be specifically hardened so that it will not deform. If and when the anvil deforms the locking action stops and the blade cannot stay open. An anvil is a large metal device or object which is used by a black smith to pound out iron or steel to different shapes. The anvil pin in a Compression lock while in theory provides a compression surface, actually deforms and pounds the tang liner and the surface of the anvil pin out of shape much as a black smith does to regular steel and iron on his anvil. The biggest problem of a compression lock is that it needs to compress against a set anvil pin. Remove that pin, deform that pin and the compression lock fails to be a lock at all. In the compression lock, the normal stop pin is a two function pin serving s stopping the rotation of the blade and the compression backing on the blade and tang or ball itself.
The further development of a compression lock is that a ball is driven onto the shelf on the butt end of the blade by a spring and the ball is compressed between the anvil pin and the blade shelf. The ball rests on only two small points top and bottom in its action to keep the blade open. Not only does this have the same weaknesses as the basic compression lock but the lock releases by pulling on the exposed sides of the ball. In hard use or under duress one might actually disengage the lock and close the blade onto one's own fingers because of inadvertent pulling on the ball. The springs might fail or become trapped with foreign material stopping the lock from engaging.
There are many other types of locking mechanisms that use springs, rotating pieces, as well as complex mechanisms using springs and balls, and rotating disks, all of which are designed to prevent inadvertent closing of the knife blade. None of these mechanisms are simple in manufacture or use. All of them are expensive to manufacture and all work on the complexity factor which in chaos theory means the more complex something is, the easier it is to fail, for only a small part has to fail to make the whole mechanism inoperative. Therefore, there is a real need for a type of folding knife locking mechanism which is simple to use, simple to make and manufacture and provides real time strength, reliability and will prevent inadvertent blade closure under use, hard use or simple handling of the blade. It must be able to be closed in a user position without releasing ones grip on the tool.
In today's world, many folding knives are in use as Self Defense Response (SDR) tools, or Full Force Continuum tools and need to be used as most folding knives cannot be used, that is, putting extreme pressure against the back edge of the knife during use. The locking mechanisms in use today are not designed for leverage or force against the back of the blade, most or all will fail immediately, inadvertently closing on ones fingers. All existing locking mechanisms demand one remove one's hands from a user position to disengage the lock. Some releases actually need two hands to disengage the locking mechanism and even those that might be able to disengage with one hand all need two hands to safely disengage the locking mechanism.
The locking mechanism described below is designed to provide an answer to these issues.